1. Field of the Invention
This invention relates to a circuit arrangement for the control of semi-duplex transmission systems in the case of crypto operation, and more particularly to such systems in which the data of a data source are supplied to a data terminal by way of a transmitting and a receiving side crypto device.
2. Description of the Prior Art
As is well known in the art, a character adapted stopping and starting of crypto generators in the case of transmission direction change in semi-duplex connections is effected with the help of an order block. The order block, consisting of several bit groups, is transmitted by the transmitting side crypto device and causes the character-correct stopping of the receiving side crypto generator. Simultaneously, with the transmission of the order block, the transmitting side crypto generator is also character-correct stopped. In the case of the transmission of desired bit sequences, it can generally not be avoided that bit patterns occur which accidentally equal the order blocks. In the case of prior art data transmission systems of this type, such inadvertently occurring order blocks cause an undesired stopping of the crypto generators, a situation which is generally reversed by the action of operating personnel. This undesired stopping of the crypto generators diminishes the effectiveness of the transmission system.